Concurrent microdeletion and duplication of 22q11.2.

Microduplication of 22q11.2 has been reported in fewer than 40 cases, all of them including the DiGeorge critical region (DGCR). We here present the characterization of a new duplication that does not include the DGCR. The duplication was initially found by multiplex ligation-dependent probe amplification analysis of 22q11.2 in a young girl with a concurrent deletion of the DGCR in 70% of her peripheral blood lymphocytes. Her phenotype included many of the features of the velocardiofacial syndrome, with velopharyngeal insufficiency, recurrent infections, learning and concentration problems as well as difficulties in social interactions. However, there were no congenital malformations, and her facial appearance was not typical for the syndrome. Further investigations included array comparative genomic hybridization (CGH) to size map the deletion/duplication and interphase fluorescent in situ hybridization to investigate mosaicism and the structure of the rearrangement. An identical duplication of this part of 22q11.2 has not been reported before, and the duplication itself seems to be associated with very mild or no symptoms. This study contributes to the growing knowledge regarding new deletions and duplications of 22q11.2, most of them mediated by the pre-disposing high number of low-copy repeats in the region.